He wrote “state” and “pensions” and drew arrows in a diagram. He wrote several phrases — “how much?” “timeline,” “what about fed gov,” “foundations,” “private sources.”

Sixteen months later, Rosen’s idea became the central element of a blueprint to reinvent one of America’s iconic cities. The unprecedented deal that Rosen imagined ultimately brought together a unique coalition of foundations, state government, unions and others to save the museum — and throw a lifeline to thousands of Detroit pensioners.

This is the backstory of how Detroit cleared mountains of debt accumulated over 50 years and emerged with a shot at restoring basic services for 685,000 city residents who deserve better. It’s a story that played out in dozens of little dramas, including the $100-Million Cab Ride, the Christmas Eve Massacre, the Mad Race to the Courthouse and the Haircut at the Haircut — when lawyers decided in a barbershop how to trim millions in Detroit debt.

And, ultimately, it’s the story of how, one by one, like soldiers switching sides in the midst of battle, the major players and creditors at war with the city dropped their objections and joined a “grand bargain” to save Detroit.